Responses of respiratory neurons in the medulla oblongata to stimulation of the septal nuclei during hypoxia.

Dynamic studies were performed in conditions of hypoxia on the effects of stimulation of the ventral, lateral, and medial nuclei of the septum on the spike activity of bulbar respiratory neurons and respiration. The various phases of hypoxia provided a model experiment over which the overall effects of the septal neurons were summed. Electrical stimulation of these septal nuclei in conditions of normal atmospheric pressure had both facilitatory and inhibitory effects on the spike activity of respiratory neurons in the respiratory center of the medulla oblongata, inhibitory effects being predominant. The ventral nucleus had the most effective inhibitory effect on the activity of respiratory neurons. Electrical stimulation of the septal nuclei in the initial phase (4000-5000 m) of hypoxia, on the background of activation, had a predominantly inhibitory influence on the activity of respiratory neurons. During the phase of severe hypoxia (7500-8000 m), on the background of marked hypoxic suppression of respiratory neuron activity, stimulation of the septal nuclei produced no characteristic changes in the activity of these neurons.